The present invention relates to surgery and particularly to electrosurgical devices.
In general when performing any surgery the surgeon must be attentive to the presence of blood vessels in the tissue being cut. Depending on the circumstances, vessels may be tied off at two positions before being severed, or if severed unknowingly, may be stapled, clipped, tied off and/or coagulated after cutting. Several surgical instruments address commonly arising situations, for example by providing dual rows of staples surrounding a cutting blade to simultaneously sever and close a vessel or tubular organ. Furthermore, electrocoagulation has been used to seal vessels and prevent the flow of blood when cut. However coagulation relies upon generation of heat in the tissue by current flowing therein, and the degree of coagulation results from a complex balance of tissue impedance, heat transfer due to contact, perfusion etc., and the area and energy of the applied RF coagulation source, all of which will affect the degree of coagulation and the time required for effective treatment. In addition to RF coagulation, RF scalpels have also come into wide use. These operate by providing a high current over a sharp edge or small area so that the contact electrode acts as a blade and cuts tissue along the blade path. The contact electrode for an RF scalpel may in fact be blade shaped, and also perform physical cutting, although in practice such scalpels have an edge of finite width to present a defined level of electrical power.
One would expect that since an electrosurgical scalpel and a coagulation unit each rely on the provision of RF energy, combined instruments would be readily available. There have in fact been instruments designed for both purposes, for example a spatula-like scalpel which is useful both for small cauterization and for cutting operations. In general however, for larger surgery, suturing or clipping of vessels is still required prior to cutting tissue or vessels. Thus, when operating in the mesentery, each vessel must be hand-tied in two places with sutures before a cut is made e.g., with scissors between the sutures, a tedious and time consuming process. One commercial product known as the "harmonic scalpel" marketed by Ethicon includes a blade and a coagulator arranged to simultaneously seal and cut sections of tissue and small vessels, thus providing an alternative to the suturing approach. However that device, configured for endoscopic use, is most suitable for procedures such as splenectomy, adrenalectomy, and breast biopsy. It operates rather slowly and its body gets quite warm during operation, raising a risk of damaging nearby tissue. Thus caution must be taken during use to avoid unintentional contact, and the practical length of the operating area is limited, making it unsuitable for many surgeries.
It would therefore be desirable to provide an electrosurgical scalpel and coagulator which operates in other tissue areas and which for example may be used to simultaneously cut and seal multiple vessels of the mesentery. It would further be desirable to provide such an instrument which coagulates quickly while producing little heat in the body of the instrument so that it may be used for prolonged periods in operation on major tissue structures such as the colon, small bowel, lungs, stomach or uterus, as well as smaller structures.